Variable and Constant Declarations
| variable | constant | type synonym | |
|---|---|---|---|
| ALGOL 68 | modename name «:= initial_value»; | modename name = value; | mode synonym = modename; |
| C (C99) | type name «= initial_value»; | enum{ name = value }; | typedef type synonym; |
| Objective-C | |||
| C++ | const type name = value; | ||
| C# | type name «= initial_value»; or var name = value; |
const type name = value; or readonly type name = value; |
using synonym = type; |
| D | type name «= initial_value»; or auto name = value; |
const type name = value; or immutable type name = value; |
alias type synonym; |
| Java | type name «= initial_value»; | final type name = value; | |
| JavaScript | var name «= initial_value»; | const name = value; | |
| Go | var name type «= initial_value» or name := initial_value |
const name «type» = initial_value | type synonym type |
| Common Lisp | (defparameter name initial_value) or (defvar name initial_value) or (setf (symbol-value 'symbol) initial_value) |
(defconstant name value) | (deftype synonym 'type) |
| Scheme | (define name initial_value) | ||
| ISLISP | (defglobal name initial_value) or (defdynamic name initial_value) |
(defconstant name value) | |
| Pascal | name: type «= initial_value» | name = value | synonym = type |
| Visual Basic | Dim name As type | Const name As type = value | |
| Visual Basic .NET | Dim name As type«= initial_value» | Imports synonym = type | |
| Python | name = initial_value | synonym = type | |
| S-Lang | name = initial_value; | typedef struct {...} typename | |
| Fortran | type name | type, PARAMETER :: name = value | |
| PHP | $name = initial_value; | define("name", value); const name = value (5.3+) |
|
| Perl | «my» $name «= initial_value»; | use constant name => value; | |
| Perl 6 | «my «type»» $name «= initial_value»; | «my «type»» constant name = value; | ::synonym ::= type |
| Ruby | name = initial_value | Name = value | synonym = type |
| Windows PowerShell | «» $name = initial_value | ||
| OCaml | let name «: type ref» = ref value | let name «: type» = value | type synonym = type |
| F# | let mutable name «: type» = value | ||
| Standard ML | val name «: type ref» = ref value | val name «: type» = value | |
| Haskell | «name::type;» name = value | type Synonym = type | |
| Forth | VARIABLE name (in some systems use value VARIABLE name instead) | value CONSTANT name |
^a Pascal has declaration blocks. See Comparison of programming languages (basic instructions)#Functions.
^b Types are just regular objects, so you can just assign them.
^c In Perl, the "my" keyword scopes the variable into the block.
^d Technically, this does not declare name to be a mutable variable—in ML, all names can only be bound once; rather, it declares name to point to a "reference" data structure, which is a simple mutable cell. The data structure can then be read and written to using the ! and := operators, respectively.
Read more about this topic: Comparison Of Programming Languages (basic Instructions)
Famous quotes containing the words variable, constant and/or declarations:
“Walked forth to ease my pain
Along the shore of silver streaming Thames,
Whose rutty bank, the which his river hems,
Was painted all with variable flowers,”
—Edmund Spenser (1552?–1599)
“But labor of the hands, even when pursued to the verge of drudgery, is perhaps never the worst form of idleness. It has a constant and imperishable moral, and to the scholar it yields a classic result.”
—Henry David Thoreau (1817–1862)
“I judge a man by his actions with men, much more than by his declarations Godwards—When I find him to be envious, carping, spiteful, hating the successes of others, and complaining that the world has never done enough for him, I am apt to doubt whether his humility before God will atone for his want of manliness.”
—Anthony Trollope (1815–1882)